The present invention relates generally to a system for checking gas pressure and gas leakage. More specifically, the present invention relates to a system that detects a state of gas pressure in a gas storage unit that functions as a main gas supply during an ion-implantation process. The system also monitors for gas leaks from the gas storage unit and informs the semiconductor manufacture process manager of the results of this checking and monitoring using a communications device. This minimizes the loss of time due to equipment stoppage and protects workers from a poisonous gas in the event of any leaks.
Since gas is used as an essential material in the manufacture of semiconductor devices, it is important to ensure a continuous gas supply during a semiconductor manufacturing process. This has the desirable effect of improving the efficiency of manufacturing operation. If poisonous gas is used, however, it is also important to continually check whether of any of the poisonous gas leaks from the gas cabinet.
FIG. 1 shows a conventional ion implanter. As shown in FIG. 1, the ion implanter comprises a gas storage unit 10, a main gas supply passage 20, an ion source chamber 30, an analyzer 40, an acceleration tube 50, a focusing unit 60, and an injector 70. As shown in FIG. 2, the gas storage unit 10 includes a plurality of gas cylinders 11a, 11b, 11c, and 11d for storing the gas used as an ion source. The ion source chamber 30 admits the gas from the gas cylinders 11a-11d through the main gas supply passage 20 and ionizes the gas to create an ion beam. The analyzer 40 selects a specified ion beam from the different ion beams generated during the ionization process. The acceleration tube 50 accelerates the ion beam selected by the analyzer 40. The focusing unit 60 focuses the accelerated ion beam. And the injector 70 injects the focused ion beam into a wafer to be processed.
FIG. 2 is a schematic diagram of the gas storage unit 10 of FIG. 1. As shown in FIG. 2, the gas storage unit 10 comprises gas cylinders 11a-11d, stop valves 12a, 12b, 12c, and 12d, first measuring instruments 13a, 13b, 13c, and 13d, second measuring instruments 14a, 14b, 14c, and 14d, and sub gas supply passages 15a, 15b, 15c, and 15d. The gas cylinders 11a-11d store various gases. The stop valves 12a-12d control the gas-supply and gas-interception to the respective gas cylinders 11a-11d. The sub gas supply passages 15a-15d are connected to the respective gas cylinders 11a-11d, through which the gas in the gas cylinders flows into a main gas supply passage 20. The first measuring instruments 13a-13d and the second measuring instruments 14a-14d are each provided at the sub gas supply passages 15a-15d for measuring gas pressure when the gas is emitted to the sub gas supply passages 15a-15d by the pressure in the cylinder itself.
The operation of such an ion implanter is described below.
The gas such as BF.sub.3 or AsH.sub.3 is supplied to the ion source chamber 30 via the sub gas supply passages 15a-15d and the main gas supply passage 20. The gas is ionized in the ion source chamber 30, and is then transmitted to the analyzer 40.
Next, the classifier 40 selects an ion beam such that only .sup.+ B.sup.11 and .sup.+ As.sup.75 are chosen from the entire ion beam that results by the ionization process. This selected ion beam is then accelerated by the acceleration tube 50 using energy of about 150 to 300 kV. Subsequently, the accelerated ion beam is focused by the focusing unit 60, and is injected into the wafer by the injector 70.
This ion implanter includes many disadvantages, however. For example, it is impossible to detect when a cylinder becomes empty because no way is provided to examine the gas pressure in the cylinders. This also further complicates the management of equipment based upon the prearranged plan. Serious time loss is inescapable when more than two of the gas cylinders are empty. This time loss results from the fact that the entire device must be stopped from the time at which the gas should be changed until the examination of renewed gas pressure is completed. In addition, to properly confirm the state of gas pressure just after the gas cylinders are changed, a worker should open the gas storage unit 10 and physically observe the first and the second measuring instruments disposed on the respective cylinders. In this confirmation step, serious accidents can be occur if a poisonous gas leaks during the time when the worker has opened the gas storage unit 10.